Patterning of electroless metals by selective deactivation of catalysts

ABSTRACT

Methods and devices for patterning electroless metals on a substrate are presented. An active catalyst layer on the substrate can be covered with a patterned mask and treated with a deactivating chemical reagent, which deactivates the catalyst layer not covered by the mask. Once the patterned mask is removed, the electroless metal layer can be placed to have a patterned electroless metals. Alternatively, a substrate can be coated with a blocking reagent in a pattern first to inhibit formation of the catalyst layer before a catalyst layer can be placed over the blocking agent layer and then electroless metal layer is placed on the catalyst layer. The pattern of the blocking reagent acts as a negative pattern of the final conductive line pattern.

This application is a divisional application of U.S. patent applicationSer. No. 14/918,227 filed Oct. 15, 2015, which claims priority to U.S.Provisional Patent Application No. 62/065,879 filed Oct. 20, 2014. Wherea definition or use of a term in a reference that is incorporated byreference is inconsistent or contrary to the definition of that termprovided herein, the definition of that term provided herein is deemedto be controlling.

FIELD OF THE INVENTION

The present invention relates to methods and systems for patterningelectroless metals on a substrate. In particular, the present inventionrelates to methods and systems that utilize an inhibitor thatdeactivates catalysts in the selective area on the substrate.

BACKGROUND

The following description includes information that may be useful inunderstanding the present invention. It is not an admission that any ofthe information provided herein is prior art or relevant to thepresently claimed invention, or that any publication specifically orimplicitly referenced is prior art.

Electroless metal deposition uses a redox reaction to deposit a layer ofmetals on a substrate without passage of an electric current. In thisprocess, several types of metals can be used as catalysts for depositionof the metals. For example, palladium, platinum, silver, are well knowncatalysts for initiating electroless metal deposition on substrates. Thecatalysts facilitate initiation and subsequent deposition of electrolessmetals (e.g., copper, tin, etc.) from solutions of metal salts. Thecatalysts can be generated and deposited on a substrate in various forms(e.g., palladium can be deposited as colloidal palladium, ionicpalladium, etc.).

Creation of metal patterns on various types of substrates is anessential part of electronic systems that are used in consumer products,communications, military, medical, and other industry segments. In orderto make electronic systems more portable, mobile, functional, smaller,and less expensive, it is necessary to make a higher density, smallsized circuitry, which requires new, cost effective patternmetallization processes.

Conventional fabrication of printed circuits uses a subtractive methodof fabrication. To produce a desired copper pattern, subtractiveprocessing uses a photolithography exposure and chemical etch to removemost of the copper that was laid down. Yet, such methods are expensivebecause it wastes a large portion of copper that is removed by etchingsteps, and is also time-consuming.

Many efforts have been put forth to create metal patterns usingelectroless metal deposition. For example, a printed circuit board canbe generated by creating a negative resist pattern over the substratesurface, etching the surface, photosensitization and/orphoto-desensitization, covering and/or stripping masks, and so on. U.S.Pat. No. 3,775,121 to Sharp discloses a method of deactivating ofcatalytic species deposited on the surface, and selectively reactivatinga portion of the deactivated catalytic species using ultraviolet (UV)radiation. Similarly, U.S. Pat. No. 8,110,254 to Sharma et al disclosesa method of creating a circuit pattern by decomposing catalyticprecursor using electromagnetic radiation and energy (e.g., thermalenergy, laser, UV heaters, ion beams, e-beams, etc.) on the substrateand/or palladium precursor.

In another example, U.S. Pat. No. 3,791,340 to Ferrara discloses amethod of a depositing a metal pattern on a surface byphoto-deactivating the catalytic species using some type of UVradiation. In Ferrara, some portions of the surface are covered with amask that protects the catalytic species under the mask from beingdeactivated. U.S. Pat. No. 8,628,818 to Sharma et al. also discloses amethod of creating a circuit pattern by using a printed, removable maskover precursor according to negative of desired pattern.

However, those methods may not be used effectively for catalysts thatare not easily imageable to allow selective metallization in the form ofan image. In addition, many of those methods require multiple steps thatincrease the complexity and cost of fabrication. Thus, there is still aneed for an improved methods and systems for patterning electrolessmetals on a substrate.

SUMMARY OF THE INVENTION

The inventive subject matter provides systems and methods for patterningof electroless metals. One aspect of the invention includes a method ofpatterning of electroless metals. One embodiment of this method includesa step of placing a catalyst layer on a substrate. Once the catalystlayer is placed on the substrate, a mask layer having a circuit patternis placed over the catalyst layer to mask the active catalyst layer.Then, the area of exposed catalyst layer is deactivated usingdeactivating reagent. The mask layer is then removed and the activecatalyst layer is exposed to electroless metal composition to form apattern of the electrolessly deposited metal on the substrate.

Another embodiment of this method includes a step of placing a blockingreagent in a pattern on a substrate to form a substrate with a blockingagent layer. Then, a catalyst layer is placed over the substrate with ablocking agent layer. The blocking reagent inhibits a formation of thecatalyst layer on the blocking agent layer so that the catalyst layerthat is not placed on the blocking agent layer is active. The methodfurther includes a step of placing an electroless metal layer on thecatalyst layer.

Another aspect of the invention includes a device having an electricalconductivity in a pattern. The device includes a substrate coated with afirst layer a blocking reagent in a pattern. On the coated substrate,the device further includes a second layer of catalyst. The devicefurther includes a third layer of an electroless metal layer that isplaced over the second layer of catalyst that is active. Allpublications identified herein are incorporated by reference to the sameextent as if each individual publication or patent application werespecifically and individually indicated to be incorporated by reference.

Various objects, features, aspects and advantages of the inventivesubject matter will become more apparent from the following detaileddescription of preferred embodiments, along with the accompanyingdrawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a flowchart of one embodiment of a method ofpatterning of electroless metals.

FIG. 2 illustrates a flowchart of another embodiment of a method ofpatterning of electroless metals.

FIG. 3 illustrates one embodiment of a device having an electricalconductivity in a pattern.

FIG. 4 shows an exemplary photograph of deactivated catalytic layer andoverlaid electroless metal layer on the substrate.

FIG. 5 shows another exemplary photograph of deactivated catalytic layerand overlaid electroless metal layer on the substrate.

FIG. 6 shows an exemplary photograph of deactivated catalytic layer byblocking reagent and overlaid electroless metal layer on the substrate.

DETAILED DESCRIPTION

The present invention relates to methods, systems and devices forpatterning electroless metals on a substrate. The principles andoperations for such methods and systems, according to the presentinvention, may be better understood with reference to the accompanyingdescription and drawings.

The following discussion provides many example embodiments of theinventive subject matter. Although each embodiment represents a singlecombination of inventive elements, the inventive subject matter isconsidered to include all possible combinations of the disclosedelements. Thus if one embodiment comprises elements A, B, and C, and asecond embodiment comprises elements B and D, then the inventive subjectmatter is also considered to include other remaining combinations of A,B, C, or D, even if not explicitly disclosed.

As used herein, and unless the context dictates otherwise, the term“coupled to” is intended to include both direct coupling (in which twoelements that are coupled to each other contact each other) and indirectcoupling (in which at least one additional element is located betweenthe two elements). Therefore, the terms “coupled to” and “coupled with”are used synonymously.

In some embodiments, the numbers expressing quantities or ranges used todescribe and claim certain embodiments of the invention are to beunderstood as being modified in some instances by the term “about.”Accordingly, in some embodiments, the numerical parameters set forth inthe written description and attached claims are approximations that canvary depending upon the desired properties sought to be obtained by aparticular embodiment. In some embodiments, the numerical parametersshould be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques. Notwithstandingthat the numerical ranges and parameters setting forth the broad scopeof some embodiments of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspracticable. The numerical values presented in some embodiments of theinvention may contain certain errors necessarily resulting from thestandard deviation found in their respective testing measurements.Unless the context dictates the contrary, all ranges set forth hereinshould be interpreted as being inclusive of their endpoints andopen-ended ranges should be interpreted to include only commerciallypractical values. Similarly, all lists of values should be considered asinclusive of intermediate values unless the context indicates thecontrary.

As used in the description herein and throughout the claims that follow,the meaning of “a,” “an,” and “the” includes plural reference unless thecontext clearly dictates otherwise. Also, as used in the descriptionherein, the meaning of “in” includes “in” and “on” unless the contextclearly dictates otherwise.

All methods described herein can be performed in any suitable orderunless otherwise indicated herein or otherwise clearly contradicted bycontext. The use of any and all examples, or exemplary language (e.g.,“such as”) provided with respect to certain embodiments herein isintended merely to better illuminate the invention and does not pose alimitation on the scope of the invention otherwise claimed. No languagein the specification should be construed as indicating any non-claimedelement essential to the practice of the invention.

Groupings of alternative elements or embodiments of the inventiondisclosed herein are not to be construed as limitations. Each groupmember can be referred to and claimed individually or in any combinationwith other members of the group or other elements found herein. One ormore members of a group can be included in, or deleted from, a group forreasons of convenience and/or patentability. When any such inclusion ordeletion occurs, the specification is herein deemed to contain the groupas modified, thus fulfilling the written description of all Markushgroups used in the appended claims.

One aspect of the present invention includes a method of patterning ofelectroless metals using electroless plating. Electroless plating uses aredox reaction to deposit metal on an object without the passage of anelectric current. One of the main advantages of electroless plaiting isthat it allows a constant metal ion concentration to bathe all parts ofthe object. Thus, electroless plating allows electroless metal to bedeposited evenly along edges, inside holes, and over irregularly shapedobjects, which are difficult to plate evenly with electroplating.

The present invention solves the problem of higher density metallizationby selectively preventing metallization. It is known in the art thatsome precious metals are catalysts for the deposition of electrolessmetals, and various forms of these catalysts have been used for years infabricating printed circuit boards using subtractive etch processes.More recently, a new method of fabricating printed circuits using aprecursor ink comprising palladium has been developed. The precursor inkis imageable, and therefore selectively allows the deposition of anatomic layer of a catalyst on a substrate that then causes copper andother metals to be deposited on the pattern made by the catalyst layer.Therefore, if the pre-cursor ink is imaged into a pattern, the copper isdeposited accordingly on that pattern.

The present invention provides alternative ways to fabricate printedcircuits, by selectively deactivating the catalytic properties of theprecursor ink, and thereby prevent the deposition of copper and othermetals on the precursor ink. Imaging this new catalyst blocker substancewith a negative image of the metalized pattern can therefore create thesame metalized pattern as that of positively imaging the precursor ink.

FIG. 1 illustrates one preferred embodiment of method 100 of patterningan electroless metal using electroless plating. In this embodiment, themethod begins with a step of depositing catalyst precursor on thesubstrate 105 to form a substrate that is at least partially coated withthe catalyst layer. Any suitable types of material, rigid or flexible,can be used as a substrate. For example, a substrate can comprise amaterial of polyimide, a cloth, a plastic, a metal, a ceramic, and aresin. It is further contemplated that many precious metals can be usedas catalyst for electroless plating, including for example, palladium,gold, silver, tin, and platinum.

In a preferred embodiment, the catalyst precursor includes elemental andactive palladium. The active palladium approximately has a zero valance.The active palladium is also ideally generated or otherwise disposedmono-atomically onto the substrate. Elemental palladium does not readilybind to a surface mono-atomically or with an approximately zero valance,and needs to be deliberately processed to achieve such a state.

The catalyst precursor may be deposited as a solution. For example, apalladium precursor solution can be prepared to include a Lewis baseligand and a palladium compound in a solvent. In a specific embodiment,the palladium precursor solution is prepared in a form of palladiumpropionate (e.g., palladium (II) propionate-cyclopentylamine complex,etc.). Additional details on preparing a palladium propionate solutionare described in the U.S. Pat. No. 8,628,818, which is incorporatedherein by reference in its entirety herein.

The catalyst precursor or a catalyst precursor solution can be deliveredto a substrate in any number of different manners. For example, thecatalyst precursor can be blanket deposited, without a pattern onto thesubstrate to deposit the catalyst precursor. In other embodiments, thecatalyst precursor solution can be delivered only to selective regionsof the substrate according to a desired pattern.

A blanket deposition involves coating a large portion or the entiresubstrate surface with the palladium ink and without defining a pattern.Dip coating represents one suitable method for blanket deposition ofpalladium ink. Dip coating allows substrates of any shape and size tohave the palladium precursor solution disposed thereon. For example,strands and fibers such as those later weaved together may bedip-coated, in addition to non-flat surfaces.

In one embodiment, the printing apparatus permits conformal printing ofthe precursor. Conformal printing refers to printing precursor onnon-flat and three-dimensional surfaces. For example, the non-flatsurface may include the inner surface of a cell phone housing or otherportable electronic device, which is commonly curved and custom shaped.In one embodiment, conformal printing apparatus includes a pen, movablein three dimensions, that dispenses palladium ink in response to acontrol signal. Based on a known position of the controlled pen relativeto the non-flat substrate, ink is released at controlled times and apattern is then produced on the conformal surface as desired.

It is especially preferred that the catalyst layer has an averagethickness of less than 10 atoms, more preferably less than 5 atoms, andmost preferably less than 3 atoms. In some embodiments, the thickness ofthe catalyst layer is achieved by modulating the concentration ofcatalyst metals in the solution. For example, it is preferred that apalladium propionate solution contains palladium in a concentration lessthan 10,000 ppm, more preferably 7,000 ppm, most preferably, less than5,000 ppm.

Once the catalyst layer is placed on the substrate, the method continueswith a step of placing a layer of patterned mask on the catalyst layer110. In a preferred embodiment, the mask includes a negative pattern ofthe final conductive line pattern (e.g., a circuit pattern, etc.). Thenegative pattern is a pattern that is substantially opposite to what thefinal conductive line pattern will be on the substrate. In essence, theareas not covered by the negative pattern will be the areas whereplating or printing of the conductive lines will occur. In someembodiments, the negative pattern is in two-dimensional (X-axis andY-axis). In other embodiment, it is contemplated that the negativepattern is in three-dimensional (X-, Y-, and Z-axis).

The negative pattern of the mask can be created by various printingtechniques. For example, conventional inkjet printers may be used topattern the removable mask. It is also contemplated that any suitabletypes of printing technique can be used to generate the pattern: screenprinting, pad-printing, Gravure printing, a stencil, rotogravure,flexographic techniques, brush coating, or various other blank coatingtechniques.

It is contemplated that any suitable types of material can be used as amask. Yet, it is especially preferred that the mask comprises a materialthat is removable from the substrate. For example, the mask can comprisea resin or polymeric material that is dissolvable in an organic solventand is insoluble in water and electroless metal solution (e.g.,Elvacite™ 2046 dissolved in methyl ethyl ketone (MEK), etc). However, insome embodiments, it is contemplated that a mask can comprise anymaterial that is at least partially dissolvable in an aqueous solution.

After the mask is placed on the catalyst layer, the method continueswith a step of treating the substrate with a layer of catalyst and alayer of patterned mask with a deactivating chemical reagent 115. Manycatalyst metals, such as palladium, platinum, silver, gold, are known tobind well to sulfur containing compounds and in general to thechalcogenides. A chalcogenide is a chemical compound consisting of atleast one chalcogen anion and at least one more electropositive element,which includes sulfides, selenides, and tellurides chemicals. Becausesulfur containing compounds or chalcogenides can bind to palladium orother types of catalysts, sulfur containing compounds and chalcogenidescan act as deactivating chemical reagents that can inhibit the catalystmetals from acting as a catalyst for the electroless copper plating.Thus, the portion of the catalyst layer that is not covered by a masklayer, and treated with a deactivating chemical reagent, would bedeactivated.

Organo disulfides, diselenides or tellurides or mixtures thereof canalso be used as potential deactivating agents that may combine with thecatalyst thus disabling its ability to initiate the electroless metaldeposition.

In some preferred embodiments, the sulfur containing compounds thatoperate as deactivating chemical reagents include yellow ammoniumsulfide, potassium polysulfide or antimony pentasulfide (Sb₂S₅).However, it is contemplated that any suitable sulfur containingcompound(s) that can deactivate the catalyst can be used as adeactivating chemical reagent.

Once at least a portion of the catalyst layer is deactivated by treatingwith a deactivating chemical reagent, the method continues with a stepof removing the layer of patterned mask 120. Then, the method continueswith a step of placing a layer of electroless metal on the layer ofcatalyst 125. While any suitable types of methods for various types ofelectroless metals (e.g., copper, nickel, etc.) can be utilized, it ispreferred that the substrate with the catalyst layer is bathed or dippedinto an electroless metal solution (e.g., a solution of electrolesscopper, M-22, supplied by MacDermid, Inc.).

Alternatively, instead of using the mask layer with a pattern to cover aportion of the catalyst layer, the catalyst layer can be selectivelydeactivated by applying the deactivating chemical reagent(s) in apattern, either in a solution or a paste form.

FIG. 2 illustrates another preferred embodiment of method 200 ofpatterning of electroless metals using electroless plating. In thisembodiment, the method begins with a step of depositing blocking reagenton the substrate to for a blocking reagent layer 205. In a preferredembodiment, the blocking reagent includes copper (II) sulfide (CuS),antimony pentasulfide (Sb₂S₅), and other metal sulfides such as iron,tin, copper, antimony, titanium, zirconium, niobium, etc. The blockingreagent can be used in a liquid form (e.g., dissolved in a solvent) orin a paste form (e.g., mixed with resin, epoxy, or other types ofpolymer, etc.). In a preferred embodiment, the blocking reagent layer isthen cured on the substrate at a temperature of at least 80 degreeCelsius, at least 100 degree Celsius, or at least 120 degree Celsius.

In some embodiments, the blocking reagent layer can be printed in apattern on the substrate using various printing techniques. For example,conventional inkjet printers may be used to pattern the removable mask.It is also contemplated that any suitable types of printing techniquecan be used to generate the pattern: screen printing, pad-printing,Gravure printing, a stencil, rotogravure, flexographic techniques, brushcoating, or various other blank coating techniques.

Optionally, once the blocking reagent layer is placed on the substrate,the method can include a step of removing excessive blocking reagentfrom the substrate by rinsing with rinsing reagent (e.g., a de-smearchemical solution, deionized water, etc.).

Once the patterned blocking agent layer is placed on the substrate, themethod continues with a step of placing a layer of a catalyst (e.g.,palladium, gold, silver, tin, platinum, etc.) on the substrate having ablocking agent layer 210. Because the blocking reagent blocks or atleast substantially inhibits formation of an active catalyst layer, theactive catalyst layer can only be significantly formed on the area ofthe substrate where the blocking reagent layer is not deposited. In someembodiments, the blocking reagent layer allows less than 10% of activecatalyst layer formed, preferably less than 5%, more preferably lessthan 1% of catalyst layer formed, compared to the area not coated withthe blocking reagent layer.

Then, the method continues with a step of placing an electroless metallayer (e.g., copper, nickel, etc.) on the catalyst layer 215. Asdescribed above, while any suitable methods for depositing various typesof electroless metals can be utilized, it is preferred that thesubstrate with the catalyst layer is bathed or dipped into anelectroless metal solution (e.g., a solution of electroless copper,M-22, supplied by MacDermid Inc.).

The use of the blocking reagent can provide several very significantbenefits in fabricating the circuit patterns. First, it provides a wayto selectively deposit electroless metals in locations and patterns thatmight be difficult or impossible through a positive imaging of thecurrently available precursor ink alone. Second, it provides analternative way for creating a pattern of the catalyst layer using anegative imaging concept. This new blocking reagent can also be used onother catalytic materials and processes that are not easily imageable toallow selective metallization in the form of an image by its blockingfunctionality. Further, it can provides an additional benefit for theindustry as it would allow the simplification of multi-layer printedcircuit board manufacturing processes that by providing a moreefficient, simpler, and less expensive method of creating functionalvias by metalizing only portions of through hole vias rather than aseries of blind and hidden vias.

Another aspect of the present invention includes a device 300 having anelectrical conductivity. FIG. 3 illustrates a diagram of the device 300.The device 300 includes a substrate 305 (e.g., a polyimide, a cloth, afiber, a plastic, a paper, a metal, a ceramic, and a resin, etc.) coatedwith a blocking reagent 310 (white, dotted) (copper sulfide (CuS) orAntimony Pentasulfide (Sb2S5), etc.) in a pattern. The device 300further includes a catalyst layer 315 (e.g., palladium, gold, silver,tin, platinum, etc.), on the substrate 305. Because the blocking reagentinhibits, deters, or at least reduces the formation of active catalystlayer 315, active catalyst layer 315 can be only formed on the area ofthe substrate 305 where the blocking reagent layer 310 is not laid on.Thus, the pattern of the catalyst layer 315 on the substrate 305 isopposite to the negative pattern of the blocking reagent layer 310.

The device 300 further includes an electroless metal layer 320 (e.g.,copper, nickel etc.) on the catalyst layer 315. Because the electrolessmetal layer 320 can be formed on the catalyst layer 315, but noteffectively on the blocking reagent layer 310 that is absent of thecatalyst layer, the pattern of the electroless metal layer 320 isaccording to the catalyst layer 315 that is opposite to the negativepattern of the blocking reagent layer 310.

This conductive pattern formation is suitable for use in circuitmanufacture, and can be used widely to create both existing and newcircuitry products. For example, the present invention enables and easesprinting of conductive lines onto flexible substrates and substrateswith custom shapes.

EXAMPLES

We have successfully used palladium (II) propionate and its complexes todeposit active palladium on substrates for electroless copperdeposition. The field coated active palladium layer can be selectivelydeactivated by using sulfur compounds such as yellow ammonium sulfide orpotassium polysulfide, etc. Selective patterning can be performed bymasking the active layer of palladium deposited on a substrate by usingmasking agents that are benign to active palladium. The areas havingunmasked palladium layer can be exposed to a solution of potassiumpolysulfide or yellow ammonium sulfide which deactivate the catalyticpalladium. The benign masking agents can now be removed to expose activepalladium followed by electroless metal deposition to form a pattern ofthe electrolessly deposited metal on the substrate.

Alternatively, metalized patterns for printed circuit boards can becreated with methods include (1) using photolithographic imagingcombined with subtractive etch processes; (2) direct laser imaging ofmetalized patterns by laser ablation of the metal that would have beenremoved by the subtract etch process in (1); or (3) a combination of (1)and (2) to achieve fine line geometry but not fine spaces.

The following examples illustrate the principle of catalyst deactivationfor preventing electroless metal deposition in selective areas

Example I

A substrate (e.g., a coupon) of 1 mil-thick polyimide was coated with asolution of amyl acetate containing 3000 ppm of palladium as palladium(II) propionate-cyclopentylamine complex as described in U.S. Pat. No.8,110,254, which is incorporated in its entity by reference herein, andthen heated to 300° C. for 10 minutes. A part of the substrate wasdipped in an aqueous solution of potassium polysulfide (3000 ppm) for 1minute. The substrate was then washed with deionized (DI) water andimmersed in a commercial electroless copper solution M-22 supplied byMacDermid, Inc. The part of the substrate that was dipped in thesolution of potassium polysulfide did not get deposition of electrolesscopper as shown in the FIG. 4.

Example II

A substrate (e.g., a coupon) of 1 mil-thick polyimide was coated with asolution of amyl acetate containing 3000 ppm of palladium as palladium(II) propionate-cyclopentylamine complex as described in U.S. Pat. No.8,110,254, which is incorporated in its entity by reference herein, andthen heated to 300° C. for 10 minutes. 5% Sb₂S₅ in Dimethyl sulfoxide(DMSO) heated to 160-180° C. and placed a palladium coated polyimidesubstrate (prepared as previously described) in the solution for 5-7min. A similar substrate with palladium used as a control without atreatment with Sb₂S₅. The substrate without Sb₂S₅ could be plated withelectroless copper while the Sb₂S₅ treated substrate could not be platedwith electroless copper.

Example III

A substrate of 1 mil-thick polyimide was field coated with a solution ofamyl acetate containing 3000 ppm of palladium as palladium (II)propionate-cyclopentylamine complex as described by U.S. Pat. No.8,110,254, and then heated to 300° C. for 10 minutes. The letter ‘A’ wasscribed with a 3000 ppm solution of potassium polysulfide in water onthe part of the substrate that had thermally cured active palladiumcatalyst. The substrate was washed with DI water for a minute and dippedin a solution of electroless copper, M-22, supplied by MacDermid, Inc.The area of the substrate with a subscribed letter ‘A’ did not getdeposition of electroless copper as shown in FIG. 5.

Example IV

Palladium blockers can be used in several ways to deactivate activepalladium catalyst for electroless copper deposition. Alternatively, thepresence of a palladium blocker can also be used to prevent thegeneration of active palladium that initiates electroless metaldeposition. In other words, the method to deactivate catalytic metalsdeposited on substrates can be used for preventing electroless metaland/or alloy and/or composite deposition by using suitable catalyticdeactivators.

One such palladium blocker is CuS. The following example illustrates howCuS can be used for preventing the formation of active palladiumcatalyst for electroless copper deposition.

Copper (II) sulfide was ground and kept in vacuum oven at 60° C. for 2hours. A total of 5 grams of commercially available 2-part Devcon5-Minute Epoxy™ was squeezed in two Petri dishes to keep both partsseparate from each other. 2.5 gram of CuS ground and dried above wasadded to each part separately. The powder was thoroughly mixed with eachpart to generate pastes. The pastes were then mixed with each otherquickly and then applied to an area of a substrate of an FR-4 epoxyboard. The substrate was then cured at room temperature for about 15minutes and then placed in an oven at 175° C. for 30 minutes. The couponwas then treated with commercially available Rohm and Haas de-smearchemistry available from Dow Chemical, Inc. The substrate was rinsedwith DI water and dried in a stream of air. It was then dipped in asolution of 3000 ppm of palladium (II) propionate-cyclopentylamine inamyl acetate for 30 seconds as described in Examples 1 and 3 above. Thesubstrate was initially air dried for 10 minutes and then with an airblower for another 5 minutes to drive off the solvent. It wassubsequently placed in an oven at 175° C. for 30 minutes. It was thendipped in MacDermid's M-22 electroless copper plating bath for 10minutes. Electroless copper did not deposit on the area that was coatedwith copper sulfide-epoxy paste while other parts of the coupon haddeposit of electroless copper as shown in FIG. 6. The areas that hadelectroless copper are electrically conducting while the coppersulfide-epoxy coated part showed no electrical conductivity subsequentto treatment with electroless copper solution.

It should be apparent to those skilled in the art that many moremodifications besides those already described are possible withoutdeparting from the inventive concepts herein. The inventive subjectmatter, therefore, is not to be restricted except in the spirit of theappended claims. Moreover, in interpreting both the specification andthe claims, all terms should be interpreted in the broadest possiblemanner consistent with the context. In particular, the terms “comprises”and “comprising” should be interpreted as referring to elements,components, or steps in a non-exclusive manner, indicating that thereferenced elements, components, or steps may be present, or utilized,or combined with other elements, components, or steps that are notexpressly referenced. Where the specification claims refers to at leastone of something selected from the group consisting of A, B, C . . . andN, the text should be interpreted as requiring only one element from thegroup, not A plus N, or B plus N, etc.

What is claimed is:
 1. A method of patterning of electroless metals,comprising steps of: placing a blocking reagent in a pattern on asubstrate to form a substrate with a blocking agent layer; removingexcessive blocking reagent from the substrate by rinsing with deionizedwater; placing a layer of a catalyst on the substrate having theblocking agent layer; placing an electroless metal layer on the catalystlayer; and wherein the blocking reagent inhibits formation of thecatalyst layer on the blocking agent layer.
 2. The method of claim 1,wherein the electroless metal comprises at least one of the following:copper and nickel.
 3. The method of claim 1, wherein the substratecomprises at least one of the following: a polyimide, a cloth, aplastic, a metal, a ceramic, and a resin.
 4. The method of claim 1,wherein the blocking reagent comprises at least one of the following:copper sulfide (CuS), antimony pentasulfide (Sb₂S₅), iron sulfide, tinsulfide, titanium sulfide, zirconium sulfide and niobium sulfide.
 5. Themethod of claim 1, wherein the catalyst comprises at least one of thefollowing: palladium, silver, gold, tin and platinum.
 6. The method ofclaim 1, further comprising a step of curing the substrate with ablocking agent layer at a temperature of at least 100 degree Celsius. 7.The method of claim 1, wherein the layer of the catalyst has an averagethickness of less than 80 atoms of the catalyst.
 8. The method of claim1, wherein the layer of the catalyst has an average thickness of lessthan 10 atoms of the catalyst.